Method of diesel particulate filter (dpf) to calculate actual soot load and ash load of the filter

ABSTRACT

A method to operate an internal combustion engine with a diesel particulate filter to extend the life of the diesel particulate filter by initiating active regeneration of the diesel particulate filter when the soot load of the filter exceeds a predetermined actual soot load value.

TECHNICAL FIELD

Emissions controls for Diesel engines has been the subject of great interest to operate cleaner engines and reduce overall global pollution values. As part of this effort many Diesel engine manufacturers are using after treatment systems and devices, such as Diesel Particulate Filters (DPF) to trap particulate emissions.

There is a need for determining the soot load and ash load of a DPF to better target initiation of DPF regenerations so that the soot and ash loads in the filter are recognized before they entirely exceed the filtration capability of the DPF. Over the lifetime of the filter, useable filtration area of the DPF will be reduced by ash accumulation while not reducing DPF life by subjecting it to excessive regenerations.

SUMMARY

Actual soot loading of the Diesel Particulate Filter (DPF) is generally based upon NOx emission levels, DPF temperatures, air fuel ratio, exhaust mass flow, soot emissions of the diesel fueled engine as well as the configuration of the DPF. It is desirable to have as few active regenerations of the DPF as possible to keep the fuel penalty associated with active regeneration as low as possible and to keep the aging of the exhaust aftertreatment systems to a minimum. It is known that active regenerations of the DPF can increase the exhaust temperature to as high as 650° C. This may be accomplished by injecting fuel in the exhaust pipe and oxidize the fuel across a Diesel Oxidation Catalyst (DOC), throttling the air mass flow to lower the air fuel ratio, post injection and other well known methods or combinations of all these methods.

In one non-limiting aspect, the present invention relates to a method to determine the point when an active regeneration should be initiated to reduce soot load in the exhaust after treatment system, and particularly in the DPF. The soot loading portion of the exhaust aftertreatment system is determined by reference to the soot emissions of the engine. The soot unloading portion is then determined by reference to the NOx emissions, DPF temperatures, air fuel ratio and the exhaust mass flow. The soot unloading portion is dependant upon the configuration of the DPF, and different configurations of the DPF can be accounted for by offsets or other factors of the soot unloading portion determination.

In another non-limiting aspect, the present invention includes a method for operating an electronically controlled internal combustion engine in a vehicle to with an exhaust aftertreatment including a DPF to initiate an active regeneration of the DPF. The engine is usually equipped with an electronic control unit (ECU) having memory. In one aspect, the method may comprise determining a soot loading portion of soot emissions in an engine exhaust stream, determining a soot unloading portion of soot emission in the Diesel Particulate Filter, determining whether the soot loading portion and the soot unloading portion exceed a predetermined ratio in the diesel particulate filter, and initiating an active regeneration of the Diesel particulate Filter based upon the ratio of the soot loading portion and the soot unloading portion.

The soot loading portion may be determined by comparing soot emission level values stored in memory in the ECU memory. These values may be stored in tables or in a map in the ECU memory. In another aspect, the soot loading values may be determined by determining the change in exhaust gas flow pressure through the DPF. As soot builds in the DPF, it clogs the DPF and results in a reduced exhaust gas pressure flow through the DPF. In this regard, a pressure sensor may located at the outlet of the DPF and electronically connected to the ECU provides data signals indicative of the exhaust gas flow pressure through the DPF. When it is determined that the exhaust gas flow pressure through the DPF is below a predetermined value, the soot loading portion is determined and an active regeneration may be indicated if the soot loading portion to soot unloading portion exceeds a predetermined ratio.

In another aspect, a pressure sensor may be located at the inlet of the DPF and another pressure sensor may be located at the outlet of the DPF. The pressure sensor at the DPF inlet provides data signals indicative of the exhaust gas flow pressure entering the DPF and the pressure sensor at the outlet provide data signals indicative of the exhaust gas flow pressure exiting the DPF. These exhaust gas flow pressure values may be compared to determine the soot loading portion which value can be used to determine the ratio of the soot loading portion to the soot unloading portion to determine whether to initiate an active regeneration of the DPF.

In another non-limiting aspect of the invention, the soot unloading portion may be determined using NOx emissions, Diesel Particulate Filter temperature, as well as the DPF configuration, the air fuel ratio, and the exhaust mass flow.

In another non-limiting aspect of the invention, a diesel fuel engine exhaust after treatment system including a Diesel Particulate Filter (DPF) comprising a controller configured to determine a soot loading portion of soot emissions in said engine exhaust; determine a soot unloading portion of soot emission in said DPF; determine whether a difference between said soot loading portion and said soot unloading portion exceeds a predetermined actual soot load value; and initiate active regeneration of said DPF.

These and other aspects of the invention will become apparent upon a reading of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an internal combustion engine and transmission.

FIG. 2 is a detailed view of the exhaust system depicted in FIG. 1.

FIG. 3 is a schematic representation of a Motor Control Module useful as an Engine Control Unit (ECU) in the present invention.

FIG. 4 is a software flow chart showing one embodiment of a method according to one non limiting aspect of the present invention.

FIG. 5 is an example of a soot load test to determine initiation of DPF regeneration.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a vehicle powertrain system 10 in accordance with one non-limiting aspect of the present invention. The system 10 may provide power for driving any number of vehicles, including on-highway trucks, construction equipment, marine vessels, stationary generators, automobiles, trucks, tractor-trailers, boats, recreational vehicle, light and heavy-duty work vehicles, and the like.

The system 10 may be referred to as an internal combustion driven system wherein fuels, such as gasoline and diesel fuels, are burned in a combustion process to provide power, such as with a spark or compression ignition engine 14. The engine 14 may be a diesel engine that includes a number of cylinders 18 into which fuel and air are injected for ignition as one skilled in the art will appreciate. The engine 14 may be a multi-cylinder compression ignition internal combustion engine, such as a 4, 6, 8, 12, 16, or 24 cylinder diesel engines, for example. It should be noted, however, that the present invention is not limited to a particular type of engine or fuel. The engine is cooperatively engaged by transmission 11 by a flywheel and either a clutch or a torque converter as is customary with engines and transmissions. The transmission has an ECU 13, that is in data communication with the engine control system, as will herein after be described.

Exhaust gases generated by the engine 14 during combustion may be emitted through an exhaust system 20. The exhaust system 20 may include any number of features, including an exhaust manifold and passageways to deliver the emitted exhaust gases to a particulate filter assembly 30, which in the case of diesel engines is commonly referred to as a diesel particulate filter. Optionally, the system 20 may include a turbocharger proximate the exhaust manifold for compressing fresh air delivery into the engine 14. The turbocharger, for example, may include a turbine 32 and a compressor 34, such as a variable geometry turbocharger (VGT) and/or a turbo compound power turbine. Of course, the present invention is not limited to exhaust systems having turbochargers or the like.

The particulate filter assembly 30 may be configured to capture particulates associated with the combustion process. In more detail, the particulate filter assembly 30 may include an oxidation catalyst (OC) canister 36, which in includes an OC 38, and a particulate filter canister 42, which includes a particulate filter 44. The canisters 36, 42 may be separate components joined together with a clamp or other feature such that the canisters 36, 42 may be separated for servicing and other operations. Of course, the present invention is not intended to be limited to this exemplary configuration for the particulate filter assembly 30. Rather, the present invention contemplates the particulate filter assembly including more or less of these components and features. In particular, the present invention contemplates the particulate filter assembly 30 including only the particulate filter 44 and not necessarily the OC canister 36 or substrate 38 and that the particulate filter 44 may be located in other portions of the exhaust system 20, such as upstream of the turbine 32.

The OC 38, which for diesel engines is commonly referred to as a diesel oxidation catalyst, may oxidize hydrocarbons and carbon monoxide included within the exhaust gases so as to increase temperatures at the particulate filter 44. The particulate filter 44 may capture particulates included within the exhaust gases, such as carbon, oil particles, ash, and the like, and regenerate the captured particulates if temperatures associated therewith are sufficiently high. In accordance with one non-limiting aspect of the present invention, one object of the particulate filter assembly 30 is to capture harmful carbonaceous particles included in the exhaust gases and to store these contaminates until temperatures at the particulate filter 44 favor oxidation of the captured particulates into a gas that can be discharged to the atmosphere.

The OC and particulate filter canisters 36, 42 may include inlets and outlets having defined cross-sectional areas with expansive portions there between to store the OC 38 and particulate filter 44, respectively. However, the present invention contemplates that the canisters 36, 42 and devices therein may include any number configurations and arrangements for oxidizing emissions and capturing particulates. As such, the present invention is not intended to be limited to any particular configuration for the particulate filter assembly 30.

To facilitate oxidizing the capture particulates, a doser 50 may be included to introduce fuel to the exhaust gases such that the fuel reacts with the OC 38 and combusts to increase temperatures at the particulate filter 44, such as to facilitate regeneration. For example, one non-limiting aspect of the present invention contemplates controlling the amount of fuel injected from the doser as a function of temperatures at the particulate filter 44 and other system parameters, such as air mass flow, EGR temperatures, and the like, so as to control regeneration. However, the present invention also contemplates that fuel may be included within the exhaust gases through other measures, such as by controlling the engine 14 to emit fuel with the exhaust gases.

An air intake system 52 may be included for delivering fresh air from a fresh air inlet 54 through an air passage to an intake manifold for introduction to the engine 14. In addition, the system 52 may include an air cooler or charge air cooler 56 to cool the fresh air after it is compressed by the compressor 34. Optionally, a throttle intake valve 58 may be provided to control the flow of fresh air to the engine 14. Optionally, the throttle intake valve 58 may also be provided to control the flow of EGR gases to the engine 14 or control both fresh air and EGR gases 64 to the engine 14. The throttle valve 58 may be a manually or electrically operated valve, such as one which is responsive to a pedal position of a throttle pedal operated by a driver of the vehicle. There are many variations possible for such an air intake system and the present invention is not intended to be limited to any particular arrangement. Rather, the present invention contemplates any number of features and devices for providing fresh air to the intake manifold and cylinders, including more or less of the foregoing features.

An exhaust gas recirculation (EGR) system 64 may be optionally provided to recycle exhaust gas to the engine 14 for mixture with the fresh air. The EGR system 64 may selectively introduce a metered portion of the exhaust gasses into the engine 14. The EGR system 64, for example, may dilute the incoming air charge and lower peak combustion temperatures to reduce the amount of oxides of nitrogen produced during combustion. The amount of exhaust gas to be re-circulated may be controlled by controlling an EGR valve 66 and/or in combination with other features, such as the turbocharger. The EGR valve 66 may be a variable flow valve that is electronically controlled. There are many possible configurations for the controllable EGR valve 66 and embodiments of the present invention are not limited to any particular structure for the EGR valve 66.

The EGR system 64 in one non-limiting aspect of the present invention may include an EGR cooler passage 70, which includes an EGR cooler 72, and an EGR cooler bypass 74. The EGR valve 66 may be provided at the exhaust manifold to meter exhaust gas through one or both of the EGR cooler passage 70 and bypass 74. Of course, the present invention contemplates that the EGR system 64 may include more or less of these features and other features for recycling exhaust gas. Accordingly, the present invention is not intended to be limited to any one EGR system and contemplates the use of other such systems, including more or less of these features, such as an EGR system having only one of the EGR cooler passage or bypass.

A cooling system 80 may be included for cycling the engine 14 by cycling coolant there through. The coolant may be sufficient for fluidly conducting away heat generated by the engine 14, such as through a radiator. The radiator may include a number of fins through which the coolant flows to be cooled by air flow through an engine housing and/or generated by a radiator fan directed thereto as one skilled in the art will appreciated. It is contemplated, however, that the present invention may include more or less of these features in the cooling system 80 and the present invention is not intended to be limited to the exemplary cooling system described above.

The cooling system 80 may operate in conjunction with a heating system 84. The heating system 84 may include a heating core, a heating fan, and a heater valve. The heating core may receive heated coolant fluid from the engine 14 through the heater valve so that the heating fan, which may be electrically controllable by occupants in a passenger area or cab of a vehicle, may blow air warmed by the heating core to the passengers. For example, the heating fan may be controllable at various speeds to control an amount of warmed air blown past the heating core whereby the warmed air may then be distributed through a venting system to the occupants. Optionally, sensors and switches 86 may be included in the passenger area to control the heating demands of the occupants. The switches and sensors may include dial or digital switches for requesting heating and sensors for determining whether the requested heating demand was met. The present invention contemplates that more or less of these features may be included in the heating system and is not intended to be limited to the exemplary heating system described above.

A controller 92, such as an electronic control module or engine control module, may be included in the system 10 to control various operations of the engine 14 and other system or subsystems associated therewith, such as the sensors in the exhaust, EGR, and intake systems. Various sensors may be in electrical communication with the controller via input/output ports 94. The controller 92 may include a microprocessor unit (ECU) 98 in communication with various computer readable storage media via a data and control bus 100. The computer readable storage media may include any of a number of known devices which function as read only memory 102, random access memory 104, and non-volatile random access memory 106. A data, diagnostics, and programming input and output device 108 may also be selectively connected to the controller via a plug to exchange various information there between. The device 108 may be used to change values within the computer readable storage media, such as configuration settings, calibration variables, instructions for EGR, intake, and exhaust systems control and others.

The system 10 may include an injection mechanism 114 for controlling fuel and/or air injection for the cylinders 18. The injection mechanism 114 may be controlled by the controller 92 or other controller and comprise any number of features, including features for injecting fuel and/or air into a common-rail cylinder intake and a unit that injects fuel and/or air into each cylinder individually. For example, the injection mechanism 114 may separately and independently control the fuel and/or air injected into each cylinder such that each cylinder may be separately and independently controlled to receive varying amounts of fuel and/or air or no fuel and/or air at all. Of course, the present invention contemplates that the injection mechanism 114 may include more or less of these features and is not intended to be limited to the features described above.

The system 10 may include a valve mechanism 116 for controlling valve timing of the cylinders 18, such as to control air flow into and exhaust flow out of the cylinders 18. The valve mechanism 116 may be controlled by the controller 92 or other controller and comprise any number of features, including features for selectively and independently opening and closing cylinder intake and/or exhaust valves. For example, the valve mechanism 116 may independently control the exhaust valve timing of each cylinder such that the exhaust and/or intake valves may be independently opened and closed at controllable intervals, such as with a compression brake. Of course, the present invention contemplates that the valve mechanism may include more or less of these features and is not intended to be limited to the features described above.

In operation, the controller 92 receives signals from various engine/vehicle sensors and executes control logic embedded in hardware and/or software to control the system 10. The computer readable storage media may, for example, include instructions stored thereon that are executable by the controller 92 to perform methods of controlling all features and sub-systems in the system 10. The program instructions may be executed by the controller in the ECU 98 to control the various systems and subsystems of the engine and/or vehicle through the input/output ports 94. In general, the dashed lines shown in FIG. 1 illustrate the optional sensing and control communication between the controller and the various components in the powertrain system. Furthermore, it is appreciated that any number of sensors and features may be associated with each feature in the system for monitoring and controlling the operation thereof

In one non-limiting aspect of the present invention, the controller 92 may be the DDEC controller available from Detroit Diesel Corporation, Detroit, Mich. Various other features of this controller are described in detail in a number of U.S. patents assigned to Detroit Diesel Corporation. Further, the controller may include any of a number of programming and processing techniques or strategies to control any feature in the system 10. Moreover, the present invention contemplates that the system may include more than one controller, such as separate controllers for controlling system or sub-systems, including an exhaust system controller to control exhaust gas temperatures, mass flow rates, and other features associated therewith. In addition, these controllers may include other controllers besides the DDEC controller described above.

In accordance with one non-limiting aspect of the present invention, the controller 92 or other feature, may be configured for permanently storing emission related fault codes in memory that is not accessible to unauthorized service tools. Authorized service tools may be given access by a password and in the event access is given, a log is made of the event as well as whether any changes that are attempted to made to the stored fault codes. It is contemplated that any number of faults may be stored in permanent memory, or rewritable memory, and that preferably such faults are stored in rewritable memory.

FIG. 2 is a detailed view of the exhaust system 30 as depicted in FIG. 1. Specifically, in one non limiting embodiment, a pressure sensor 41 may be positioned at the DPF inlet 39 to measure the exhaust gas flow 37 pressure in the inlet of the DPF. The pressure sensor 41 is electronically connected to the ECU and transmits data signals to the ECU indicative of the exhaust gas flow pressure. A pressure sensor 43 may positioned at the outlet 45 of the DPF to detect the exhaust gas flow pressure at the outlet of the DPF. The detected exhaust gas flow pressure at the inlet is compared to the exhaust gas flow pressure at the outlet and the comparison between the inlet exhaust gas flow pressure and the outlet exhaust gas flow pressure is made and the soot loading portion of the DPF is determined.

In another non limiting embodiment, a pressure sensor 43 is disposed at the outlet of the DPF and the exhaust gas flow pressure is compared to values stored in memory in the ECU and a determination is thereby made as to the soot loading portion in the DPF. If the soot loading portion exceeds a predetermined value, the method initiates an active regeneration of the DPF.

FIG. 3 is a schematic representation of the controller 92 of the present invention. The engine control system has a Motor Control Module 118 and a Common Powertrain Controller 120. Each of the Common Powertrain Controller and the Motor Control Module has memory for storage and retrieval of operating software and faults. The Motor Control Module and the Common Powertrain Controller (CPC2) communicate with each other via a data link, such as the electronic common area network (ECAN) 122. It is contemplated that any electronic communication between the Motor Control Module (MCM) and the Common Powertrain Controller is acceptable to communicate static faults stored in either, so that each has the most current version of the faults in the other module at any time. The Common Powertrain Controller communicates with the vehicle systems via an SAE data link J1939 and J 1587, (124 and 126, respectively) and it is contemplated that it is equally possible that the Common Powertrain Controller (CPC2) may communicate with the various vehicle systems over a UDS link.

FIG. 4 is a schematic non limiting representation of one method 128 according to the present invention. Specifically, at step 130, a determination is made regarding the soot loading portion of the diesel particulate filter. The soot loading portion is a value that represents the amount of ash and soot present in the diesel particulate filter.

In one aspect, the soot loading portion may be determined by the formula

Y_Loading=ab (X^(m) +cX ^(n))

Wherein

Y_loading=the soot loading portion

a=f_(a,) which represents a correction factor

b=f_(b) which represents Lambda, air mass flow

c=f_(c) which represents a correction factor

X=f_(x) which represents engine smoke numbers out. It is understood that the smoke of the engine can be measured in smoke numbers, filter smoke number (FSN), SZ Bosch, Celesco percent, percent Opacity, or whatever measurement can be used to quantify smoke numbers of the engine before the DPF.

It is further understood that Y loading can also be table based, wherein the values for f are held in memory for each engine operating speed and load points.

At step 132, a determination is made regarding the soot unloading portion of the DPF. The soot unloading portion represents the capability to oxidize any soot in the DPF, either by passive regeneration, (CRT effect) by increasing the engine exhaust stream temperature to the range of from about 280° C. to about 500° C. and using NO₂ to determine soot unloading according to 2 NO₂+C→2NO+CO₂, or by initiating active regeneration that increases the temperature of the exhaust stream to a range of from about 450° C. to about 650° C. by burning the soot according to C+O₂→CO₂, such that the soot is burned in the DPF to clear the passages there through. The soot unloading portion of the DPF is determined by making reference to at least one of NOx emissions, the temperature of the DPF, the air fuel rate, the exhaust mass flow and the configuration of the DPF. The soot unloading portion may be determined according to the formula:

Y_Unloading=abc X ^(n)

Wherein

a=f_(a,) which represents specific unloading factor, DPF configuration, DPF coating; those skilled in the art recognize that the DPF may be coated with various materials, such as, without limitation, platinum, or by any base materials, as is well known in the art. DPF configuration includes, without limitation, size, shape or orientation of the DPF i.e, whether oriented parallel, or serially, or in any configuration known in the art.

b=f_(b) which represents Lambda, DPF temperatures. It is contemplated that with different Lambda (or air/fuel ratios−AFR) and different exhaust temperatures the regeneration capability of the exhaust aftertreatment system (especially for the passive regeneration) is different. For example, when the exhaust flow temperature is in the range of about 400° C., the passive regeneration capability is excellent, especially in the presence of NO₂ . Accordingly, it is understood that b is a function of Lambda (AFR) and exhaust temperatures.

c=f_(c) which represents NO, NO₂ (It is to be understood that increases in NO and NO₂ are preferable, however, the preferred amount of NO and NO₂ depends upon the coating of the DPF and the DOC, as well as how well NO is converted to NO₂ to have a better passive regeneration.

X=f_(x) which represents actual soot load. It is to be understood that the soot unloading depends as well of the amount in g/l of soot load which is at that time in the DPF. The higher the soot load, the higher the passive and active regeneration capability. This means the higher the soot load, the more soot is burned under the same condition. But not all the soot is burned during the regeneration process. Whereas the great majority of the soot is burned in the DPF during regeneration, it is hard to get the remainder of the soot out of the filter if there is only a little bit soot in the filter.

Y_Unloading may also be table based, wherein the values for f are held in memory for each engine operating speed and load points.

At step 134, a determination is made whether the actual soot load portion of the DPF exceeds a predetermined value. In one embodiment, the actual soot load portion of the DPF may determined by difference between soot loading portion and the soot unloading portion. The actual soot load of the filter may be determined by the formula:

Y_Soot_Load_Actual=Y_Loading−Y_Unloading

To detect higher than usual soot load and ash load, or to detect soot load and ash load over a DPF lifetime, a pressure drop across the DPF is determined. In this embodiment, the actual soot load may be determined according to the formula:

Y _(—) ΔP _(—) DPF=ab/cd ^(n)

Wherein

a=f_(a,) which represents DPF exhaust gas flow pressure in, out, offset;

b=f_(b) which represents ambient pressure, DPF pressure in, out;

c=f_(c) which represents DPF temperatures;

d=f_(d) which represents exhaust mass flow; and

P=exhaust gas flow pressure.

To compensate for noise overlay, Y_ΔP_DPF function may be used in certain speed and load ranges only and the signal may be filtered by using a moving average. Over the lifetime of a DPF, an increase in Y_ΔP_DPF for an empty DPF (i.e., without a soot load) indicates additional pressure drop caused by ash load. This increase of Y_ΔP_DPF may further be used to initiate an ash cleaning of the filter and/or to reduce the regeneration point so that there is a specific soot load indicated before regeneration is initiated.

If the soot load portion is beyond a predetermined amount, then an active regeneration of the DPF is undertaken as at step 136. If the soot load portion is not beyond a predetermined amount, then the method loops back to step 130.

FIG. 5 is a representation of a soot load test example to determine initiation of DPF regeneration. FIG. 5 is an example of an actual engine run according to on aspect of the present invention. Specifically, at 138 the actual soot in the DPF is shown in grams. By reference to FIG. 5, it can be seen that the calculated soot load actual 140 is the same as the actual soot load. This indicates that the describe method is operational and provide the advantages previously described. In addition, it can be seen that the backpressure portion/ash detection of the soot load model (Y_ΔP_DPF) is operating.

The words used in this application are understood to be words of description, and are not words of limitation. Those skilled in the art recognize that many variations and modifications may be made without departing from the scope and spirit of the invention as set forth in the appended claims. 

1. A method to operate an electronically controlled compression ignition engine equipped with an Electronic Control Unit (ECU) and having an exhaust system including an exhaust after treatment system including a Diesel Particulate Filter (DPF); said method comprising: determining a soot loading portion of soot emissions in said engine exhaust; determining a soot unloading portion of soot emission in said DPF; determining whether a difference between said soot loading portion and said soot unloading portion exceeds a predetermined actual soot load value; and initiating active regeneration of said DPF.
 2. The method of claim 1, wherein said soot loading portion is determined according to the formula Y_Loading=ab (X^(m) +cX ^(n)) Wherein Y_Loading=the soot loading portion; a=f_(a,) which represents a correction factor; b=f_(b) which represents Lambda, air mass flow; c=f_(c) which represents a correction factor; and X=f_(x) which represents engine smoke numbers out.
 3. The method of claim 1, wherein said soot unloading portion is determined according to the formula Y_Unloading=abc X ^(n) Wherein Y_Unloading=the soot unloading portion; a=f_(a,) which represents specific unloading factor; b=f_(b) which represents Lambda, DPF temperatures; c=f_(c) which represents NO, NO₂; and X=f_(x) which represents actual soot load.
 4. The method of claim 1, wherein actual soot load of the DPF is determined according to the formula Y_Soot_Load_Actual=Y_Loading−Y_Unloading
 5. The method of claim 1, wherein a higher than normal soot and ash load in said DPF is determined according to the formula Y_ΔP_(—) DPF=ab/cd ^(n) Wherein a=f_(a,) which represents DPF exhaust gas flow pressure in, out offset; b=f_(b) which represents ambient pressure, DPF pressure in, out; c=f_(c) which represents DPF temperatures; d=f_(d) which represents exhaust mass flow; and P=exhaust gas flow pressure.
 6. The method of claim 1, wherein said soot load, soot loading portion, soot unloading portion are values in tables in memory in said ECU.
 7. A diesel fuel engine exhaust after treatment system including a Diesel Particulate Filter (DPF) comprising: a controller configured to determine a soot loading portion of soot emissions in said engine exhaust; determine a soot unloading portion of soot emission in said DPF; determine whether a difference between said soot loading portion and said soot unloading portion exceeds a predetermined actual soot load value; and initiate active regeneration of said DPF.
 8. The diesel fuel engine exhaust aftertreatment system of claim 7, wherein said soot loading portion is determined according to the formula Y_Loading=ab (X ^(m) +cX ^(n)) Wherein Y_Loading=the soot loading portion; a=f_(a,) which represents a correction factor; b=f_(b) which represents Lambda, air mass flow; c=f_(c) which represents a correction factor; and X=f_(x) which represents engine smoke numbers out.
 9. The diesel fuel engine exhaust aftertreatment system of claim 7 wherein said soot unloading portion is determined according to the formula Y_Unloading=abc X ^(n) Wherein Y_Unloading=the soot unloading portion; a=f_(a,) which represents specific unloading factor; b=f_(b) which represents Lambda, DPF temperatures; c=f_(c) which represents NO, NO₂; and X=f_(x) which represents actual soot load.
 10. The diesel fuel engine exhaust aftertreatment system of claim 7, wherein actual soot load of the DPF is determined according to the formula Y_Soot_Load_Actual=Y_Loading−Y_Unloading.
 11. The diesel fuel engine exhaust aftertreatment system of claim 7, wherein a higher than normal soot and ash load in said DPF is determined according to the formula Y_ΔP_DPF=ab/cd ^(n) Wherein a=f_(a,) which represents DPF exhaust gas flow pressure in, out offset; b=f_(b) which represents ambient pressure, DPF pressure in, out; c=f_(c) which represents DPF temperatures; d=f_(d) which represents exhaust mass flow; and P=exhaust gas flow pressure.
 12. The diesel fuel engine exhaust aftertreatment system of claim 7, wherein said soot load, soot loading portion, soot unloading portion are values in tables in memory in said controller. 